The manipulation of samples or devices through the use of electromagnetic (EM) radiation has a number of advantages over mechanical or “tactile” manipulation.
Typically, EM manipulation is less mechanically destructive and can be accomplished through mechanical barriers where other more traditional means are not effective. EM manipulation has become more prevalent as technology has advanced and is now accomplished through both constant field applications (as in the case of superconductor facilitated magnetically induced levitation) and oscillating field applications (e.g. laser assisted cooling and trapping).
The manipulation of mass through the use of laser light has found many applications as laser technology has evolved. Not simply laser photolysis or spectroscopy, but coherent control of chemical reactions is becoming possible (see P. Brumer and M. Shapiro, Sci. Am., pg. 56, March 1995). Laser atom or molecule trapping has seen a great deal of activity (see S. Chu, Science, pg. 861, 23 Aug. 1991; C. N. Cohen-Tannoudji and W. D. Phillips, Phys. Today, pg. 33, October 1990) and has lead to the observation of Bose-Einstein condensation and the improvement of atomic clocks. Control of larger mass samples with laser energy has also been demonstrated. “Optical tweezers” have been used to stretch single strands of DNA and manipulate chromosomes inside cell nuclei and move entire cellular organelles without destroying the cell wall (see S. Chu, Sci. Am., pg. 71, February 1992). Standing wave laser radiation has also been used to deflect atomic beams in flight (see P. E. Moskowitz, P. L. Gould, and D. E. Pritchard, J. Opt. Soc. Am. B., 2, 11, 1784, 1985).
All of these techniques allow for control of small samples with laser light, but none of these is practically applicable to larger samples or efficiently uses the laser light to accomplish the manipulation. One of the difficulties is that many of the current techniques operate by inducing an electric charge polarization in the sample. The force which can be induced by the laser beam is directly related to the degree to which a sample can be polarized before it is damaged. The laser peak intensity must be controlled or the sample can be overheated, ionized or destroyed. This limits the achievable manipulation force. Also, these techniques commonly require the laser to be focused on the target sample, limiting the length of interaction and thus the efficiency with which the laser energy is coupled into translation. Other techniques rely on the transfer of photon momentum in the optical scattering process, but this is extremely inefficient as photons at commonly accessible wavelengths have very little mass.
Therefore, it is the object of the present invention to provide a system that 1) employs laser light to apply a force to objects that 2) is scalable, that 3) maximizes the efficiency with which the laser light is utilized for said force, that 4) the intensity of laser light employed by the system should not be limited by the risk of damage to the object upon which the force is induced.